#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<windows.h>
#include<cmath>
using namespace std;

int main()
{
	//int a, b, c;
	//while (cin >> a >> b >> c)
	//{
	//	cout << " a=" << a << " b=" << b << " c=" << c << endl;
	//}
	//const double p = 0.065499;
	//const double pi = 3.1415926;
	//double res = 0, w0[10] , w[10] ;
	//char ch = 0;
	//int n = 10;
	//cin >> n;
	//for(int i  = 0 ; i < n ; i++)
	//{
	//	cin >> w0[i] >> w[i];
	//}

	//for (int i = 0; i < n; i++)
	//{
	//	if(w0[i]<w[i])
	//		res = atan(2 * p * w[i] / (pow(w0[i], 2) - pow(w[i], 2)))+pi;
	//	else
	//		res = atan(2 * p * w[i] / (pow(w0[i], 2) - pow(w[i], 2)));

	//	res = res * 180 / pi;
	//	cout << res << endl;
	//}

	//double a[50], b[50];
	//int n = 0;
	//cin >> n;
	//for (int i = 0; i < n; i++)
	//{
	//	cin >> a[i] >> b[i];
	//}
	//for (int i = 0; i < n; i++)
	//{
	//	cout << a[i] - b[i] << endl;
	//}


	double a[100];
	int n = 0;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> a[i];
	}
	for (int i = 0; i < n; i++)
	{
		cout << a[i] * 2 * 3.1415926;
	}
	return 0;
}